I believe one (or more) of the TPMS valves stopped functioning and the RX's ECU can't communicate with it.
Before bringing it in for servicing try this if you haven't:

Drop the tire pressure on all four tires to a significantly lower value say about 25 psi. Do the reset procedure. Then add air to the recommended 32-33 psi. Turn on the car, drive the car around for a couple miles. Then park/power off the car. Wait a couple mins, power the car back on. Result?

Manual suggests that when the light simply comes on, it's a pressure related problem. However, if it starts by blinking first followed by steady on, then it's a system problem that requires inspection. Might be something simple like a low battery alert for one of the sensors.

I believe one (or more) of the TPMS valves stopped functioning and the RX's ECU can't communicate with it.
Before bringing it in for servicing try this if you haven't:

Drop the tire pressure on all four tires to a significantly lower value say about 25 psi. Do the reset procedure. Then add air to the recommended 32-33 psi. Turn on the car, drive the car around for a couple miles. Then park/power off the car. Wait a couple mins, power the car back on. Result?

Keep us posted.

Not sure I want to do that, the reset doesn't work with 32 psi so I don't see why it will work with 25.
Thanks for the suggestion.
Like Droid13 say it may be sensor or TPM module related, so I will call the dealer tomorrow for a service appointement.

Yesterday I called the dealer for a service appointment, after I describe the problem they asked me if I had check the pressure in the spare tire!

NO... I never checked the spare, so I did like they say and check the spare pressure.

It was at 47 pounds, on the tire you can see the recommended pressure that is labeled at 60 pounds. I inflated the tire to 60 pounds and recheck my TPM light, still blinking then solid ON.

I also noticed that there doesn't seems to be a pressure monitor valve on that tire, this tire is just to get you out of trouble, it is not a regular tire.

I took my car this morning and I noticed that the warning was gone!!!!!!, I really don't understand what is happening here.

(About 6 months ago, while I was travelling in Texas I had a low tire pressure warning that went away after 1 day!!!! all tires were fine. Could be related.)

I phoned the dealer this morning and asked them what should be done with my intermittent Tpm problem. They told me there is nothing they can do if the Tpm light is Off, I suggested the 4 valves replacement.....the answer was No.

I am extremely dissapointed with Lexus service, for me this is unacceptable.
They didńt even offer to do some pressure testing in order to find a marginal valve!

This problem has happened twice and there is no reason it will not happen again.

I phoned the dealer this morning and asked them what should be done with my intermittent Tpm problem. They told me there is nothing they can do if the Tpm light is Off, I suggested the 4 valves replacement.....the answer was No.

I am extremely dissapointed with Lexus service, for me this is unacceptable.
They didńt even offer to do some pressure testing in order to find a marginal valve!

This problem has happened twice and there is no reason it will not happen again.

Don't get too stressed over it. When the light is on, you bring it in and they fix it. Sensor may be going bad and when it does, they will replace it.

Don't get too stressed over it. When the light is on, you bring it in and they fix it. Sensor may be going bad and when it does, they will replace it.

I am getting very unhappy because Lexus areńt proactive at all with their service, this is the second problem on my car were the dealer doesńt do anything.( wiper going ON for nothing, clean windsheild and no rain! , then Tpm!!)

I spend my winters in Mission, Tx. and the nearest dealer is in Houston or San Antonio, many hours from where I reside. So I am stuck with my caŕs problems.

I know those problems are minor but I was expecting a lot more from Lexus, as far as I am concerned local Lexus service sucks.

I am getting very unhappy because Lexus areńt proactive at all with their service, this is the second problem on my car were the dealer doesńt do anything.( wiper going ON for nothing, clean windsheild and no rain! , then Tpm!!)

I spend my winters in Mission, Tx. and the nearest dealer is in Houston or San Antonio, many hours from where I reside. So I am stuck with my caŕs problems.

I know those problems are minor but I was expecting a lot more from Lexus, as far as I am concerned local Lexus service sucks.

Understand your frustration. That isn't indicative of Lexus though as most dealers operate the same. If there is no actual verifiable problem presented when the vehicle is in for service, they will not repair. Have to remember that when you bring in your vehicle, you're not meeting with a technician. You're meeting with a service advisor who will likely not know any technical information about your model as they are there for intake and delivery of all model vehicles. So they write up what you tell them the issue is and send that down to the tech. The tech then duplicates your described issue, diagnoses the problem and then repairs. If there is nothing for them to diagnose, then there is not justification on their end to do any repair work.

TPMS is just a monitor and not likely to leave you stranded somewhere as you have the ability to physically check your tire pressure. If it were something serious, the vehicle would trigger a check engine light and even it is intermittent, it can be historically pulled from the car to see what went wrong. But yes, for stuff like squeaks, rattlers and the like, you need to replicate the issue.

Lepapeherm, sorry you feel that way. It's not typical Lexus service. The wiper going on for no reason is actually common. Newer RXs seem to have that problem more than older ones like mine. That and speeding up all of the sudden.

Speak to the service manager about your disappointment, not just anyone in service. Part of me doesn't want to rule out the possibility the TPMS is set too high. Dealers typically fill the tires above the recommended level. It takes about a 7-8 lb drop from the reset level before the light is supposed to turn on. And you're not stuck with the problems. We'll try to help you as much as we can.

TPMS systems can be finicky, they are foisted upon us by nanny government who figures we aren't smart enough to monitor our pressures. If it is intermittent I would grin and bear it until you take the car in for other service. As long as the pressures are correct in the tires you are ok.

I live in TX and once in awhile the wiper will make a swipe when there is no rain. This can be due to humidity or even a juicy bug that hits just in the right spot. It's really a non issue, if it bothers you just move the stalk up one notch and turn the auto system off. It's fine 99.9% of the time.

I don't think your issues are Lexus related, they relate to electronic system complexity we see in all cars. Lexus' are far better than other luxury cars in this regard.

elba123, Ray is right. I was referrig to the wiper. It typically speeds up during turns but sometimes while driving straight, not in a pouring rain. I call it the hyperwipe, LOL!

I've had the TPMS light come on three times in 11 years - once on the 330 for what turned out to be a slow leak around the weight, then twice on the 450h when the tire pressure dropped but not very low (31) and after one of the tires picked up a screw. It's worked precisely as it should, during situations I might not be immediately aware of. It's not meant to be a substitute for checking the tire pressure. Now the change oil light coming on every 5K instead of 10K in the RX is a different story..